1. Field of the Invention
This invention relates to a golf club and, more particularly, to a golf club which is advantageously used for practicing a swing movement.
2. Description of the Related Art
A golf club comprises a club head, a hollow shaft and a grip. Generally speaking, when a wood or iron club is used and a swing movement is conducted therewith, the hollow shaft is pliably bent due to the inertia force of the club head during the downswing motion, and returned to a straight status, usually, at a moment of impact with a ball. If the downswing motion is conducted in such a manner that the shaft is pliably bent to the largest extent immediately after the downswing motion is started, the speed of the club head becomes the highest at the moment of ball impact. If, however, less force is exerted on the golf club immediately after the downswing motion is started, the value of strain is less, so that the speed of the club head becomes lower at the ball impact. Similarly, if the timing at which a large force to exerted on the golf club is late during the downswing motion, the timing at which the shaft is returned to a straight status becomes inconsistent with the ball impact timing in such cases, sufficient kinetic energy may not be given to the golf ball, or the ball may travel in an undesired direction.
A golf club shaft having a grip which is provided with a strain gauge for detecting a torsion of the grip portion is known in the prior art, as disclosed in Japanese Unexamined Utility Model Publication No. 55-125369. However, in this golf club, the strain of the shaft itself during the downswing movement thereof cannot be detected.